How to Vent Behind Drywall

Locate the wall studs behind the drywall using a stud finder, and hold the vent cover on the wall where you want the return air vent. Line up the sides of the register over the wall studs. Most return air vents are 16 inches wide so they fit between standard wall studs.

Make a pencil mark on the drywall on each side of the register at the upper corners.

Use a carpenter’s level and draw a level line between the two marks you made on the wall and a bottom line. This line represents the top of the vent.

Position a T-square along the line and use the edge of the square to draw straight lines that represent the sides and the bottom of the vent cover. The side lines should be centered over the wall studs. Now you have a rectangle that represents the outside perimeter of the vent cover.

Draw a second, smaller rectangle, 1/2-inch in from the original lines, and cut out the smaller rectangular with a sharp utility knife. Remove the drywall from the hole.

Position the register over the hole, lining up the top and sides with the original pencil lines, and insert screws in the side holes, through the drywall and into the wall studs beneath. The vent may come with screws, otherwise, use wood screws that are long enough to go through the drywall and at least 1/2 inch into the studs beneath.